Entanglement Of Photon Pairs Generated From Semiconductor Quantum Dot And The Coupling Between Quantum Dot And Noble Metal Nanowire

Semiconductor quantum dots (SQDs) play key roles in quantum computation and quantum information processes, and SQD is expected to be a promising entangled-photon source. Surface plasmons (SPs) are also gained great interest for their applications in biosensors and local field enhancement. In recent years, there is a great progress in the study of the coupling between SQDs and metal nanowires to achieve relatively long range information transmission. In this paper, we have investigated the polarized entangled photon pairs generated from single SQD, the coupling between nanometer sized emitter (for example SQDs) and noble metal nanowires, and the design of nanoring biosensor and nanoring antenna. The main work is included as follows:1. Entangled photon pairs generated from SQDThe second order cross correlation functions and polarization density matrix of the biexciton system of single SQDs with pulse excitation are analyzed by using master equations and quantum regression theorem. The entanglement properties of photon pairs generated from SQD with degenerate and non-degenerate exciton states have been investigated. And the influences of spin relaxation between exciton states, spectral window width, and input pulse areas have also been discussed.2. Nanoring Multipolar SP resonances and the design of ring-biosensorThe relationships between nanoring multipolar SP resonances and SP wavelength are investigated by using discrete dipole approximation (DDA) and finite difference time domain (FDTD) methods, and a scheme has been proposed to increase the sensitivity of biosensor. The calculation results show that, for perfect nanorings, there will be a resonance when the ring circumference is about an integer times of SP wavelength, while a semi-integer for split nanorings with one gap. These relationships reveal that the refractive index sensitivities for multipolar SP resonances are proportional to their mode number’s reciprocal. And the refractive sensitivities of split nanorings at main resonance is about 100% larger than those of perfect nanorings with same size.3. Nanoring SP focusing and the design of ring-nanoantennaFor SP propagation processes that under oblique incident excitation, the energy is focusing to one side of the nanorings, and nanoring can be used as plasmonic lens. Gaps are introduced in the rings, and the local field intensity enhancement of split nanoring with three gaps has increased about 37% than that of dipole antennas.4. The coupling between nanometer sized emitter and noble metal nanowireThe coupling, propagations, and far-field emissions of SPs in a pair of Au nanowires with a dipole emitter have been investigated using the FDTD method. The SP is tunable from 652 to 380 nm by adjusting the distance between the two wires, which leads to an enhancement of coupling constant and density of states of the SP. The converted energy from the dipole emitter to the propagating SP as well as the far-field emission intensity of a pair of Au nanowires increase to approximately four times as large as those of a single nanowire.